1. Field of the Invention
The present invention relates to an optical disc drive.
2. Description of the Prior Art
There are known optical disc drives for reading out data from a read-only optical disc such as a CD-ROM and the like, and optical disc drives for recording data onto and reading out data from a recordable optical disc such as a CD-R, a CD-RW and the like.
In general, such optical disc drives include a rotational drive mechanism for rotating a loaded optical disc, an optical pick-up (optical head) which is movable in a radial direction with respect to the loaded optical disc, and an optical pick-up moving mechanism equipped with a sled motor for moving the optical pick-up in the radial direction.
The optical pick-up is constructed from an optical pick-up body (optical pick-up base) equipped with a laser diode and a split photodiode, an objective lens supported on the optical pick-up body by means of suspension springs to enable movement in the optical axis direction (focus direction) and the radial direction with respect to the optical disc, and an actuator for moving the objective lens in the optical axis direction and the radial direction.
In such optical disc drives, first, the optical pick-up is moved to a target track (target address). At the target track, data is recorded (written) onto the optical disc and/or read out (reproduced) from the optical disc with focus control operation and tracking control operation being carried out.
In these disc drives, in order to transmit data at a higher data transfer rate, it is required that the optical disc is rotated at a high speed.
However, when an optical disc is rotated at a high speed, there is a case that a proper play back can not be made (data can not be properly read out from the optical disc), that is there is a case that a read error occurs, due to flaws or dirty portions on the recording surface of the optical disc. Even though the degree of such flaws or dirty portions is negligible under the low rotation speed, such flows or dirty portions are like to affect reading out of data under the high rotation speed. If such a read error occurs when the optical disc is to be played back, it becomes impossible to read out proper data from the optical disc.
In this regard, frequency of the occurrence of the read error can be reduced by using a lower rotation speed for rotating the optical disc, but this in turn has the disadvantage of lowering a data transfer rate.
It is therefore an object of the present invention to provide an optical disc drive capable of reliably reading out data from an optical disc in a shorter period of time.
In order to achieve the above object, the present invention is directed to an optical disc drive which can at least read out data from an optical disc when the optical disc is loaded into the optical disc drive, the optical disc drive comprising:
a rotational drive mechanism for rotating the loaded optical disc at a predetermined rotation speed which is one of multiple rotation speed levels;
an optical pick-up for reading out data from the optical disc which is rotated by the rotational drive mechanism;
judgement means for making a judgement as to whether the data has been properly read out from a predetermined portion of the optical disc; and
retry control means for lowering the rotation speed of the optical disc from the predetermined rotation speed when the judgement means has judged that the data was not properly read out from the portion of the optical disc, and then for retrying to read out the data from the same portion of the optical disc rotating at the lowered rotation speed.
As was described above, according to the present invention, in the case where the judgement means of the optical disc drive has judged that data was not properly read out from a portion of an optical disc, the optical disc drive lowers a rotation speed of the optical disc and then retry to read out the data from the same portion of the optical disc. This allows data to be reliably read out from an optical disc in a shorter period of time.
In this invention, it is preferred that the judgement means is designed to make a judgement that data has not been properly read out from the portion of the optical disk when the data could not be properly read out in spite that trial has been made at least two times to read out the data from the same portion of the optical disc rotating at the predetermined rotation speed.
In this case, it is preferred that the predetermined rotation speed of the optical disc is normally set at the maximum rotation speed level in the multiple rotation speed levels.
In the present invention, it is preferred that when the judgement means has judged that the data was not properly read out from the portion of the optical disc, the retry control means lowers the rotation speed of the optical disc by one level from the predetermined rotation speed level and then retries to read out the data from the same portion of the optical disc rotating at the lowered rotation speed.
In this case, the retry control means may be designed to lower the rotation speed of the optical disc one level by one level in the multiple rotation speed levels and then retries to read out the data from the same portion at each of the lowered rotation speed levels until the data can be read out from the same portion of the optical disc.
Further, in the present invention, it is preferred that the retry control means includes means for returning the lowered rotation speed level to the previous rotation speed level. In this case, it is preferred that the previous rotation speed level is the maximum rotation speed level.
Furthermore, it is also preferred that the rotation speed of the optical disc is adapted to be set at the maximum rotation speed level, when data of a different portion of the optical disc is to be read out by moving the optical pick-up over one truck or more.
Moreover, it is preferred that the optical disc drive further comprises signal output means for outputting signal indicating that an error has occurred during reading out the data, wherein the signal output means outputs the signal when the judgement means has judged that the data was not properly read out from the optical disc in spite that the retry control means lowers the rotation speed to the lowest rotation speed level in the multiple rotation speed levels and then retries to read out the data from the same portion of the optical disc.
These and other objects, structures and advantages of the present invention will be apparent from the following description of the preferred embodiment when it is considered taken in conjunction with the appended drawings.